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Re: [Xen-devel] Credit Scheduler not working correct (3.0.4-0)

Ok so If I get this right, what you want to do is have 2 UP guests with
different weights. You also want to turn off HT and you do this by
pinning both guests on CPU 0.

Credit accounting and pinning VCPUs don't always interact well
and I suspect you're hitting such a problem here.

If you have access to the Xen console, can you send output of
the 'r' (runq) key while your domains are each getting 50% of
CPU? Just take a few snapshots a few seconds apart. That would
confirm the theory.

Also, setting cap=100 on a UP guest is pointless. Just leave it
as zero. A VCPU isn't going to get more than 100% of a physical
CPU anyway.

On Feb 1, 2007, at 10:47, Timo Benk wrote:

on my system, it seems that the credit scheduler does not work as expected. The problem seems to be related to HyperThreading, if i switch off HT in the BIOS
Setup, the scheduler works as expected.

I have two domains running, both pinned to the same processor:

Domain-0:~ # xm vcpu-list
Name                              ID  VCPU   CPU State   Time(s) CPU
Domain-0 0 0 1 --- 30.2 any cpu Domain-0 0 1 1 r-- 12.0 any cpu
xendom1                            1     0     0   ---      98.6 0
xendom2                            2     0     0   r--     110.3 0

Both domains should consume max. 100 Percent of that processor, but
xendom1 has a weight twice as big as xendom2:

Domain-0:~ # xm sched-credit -d xendom1
{'cap': 100, 'weight': 200}
Domain-0:~ # xm sched-credit -d xendom2
{'cap': 100, 'weight': 100}

In my understanding of the credit scheduler, xendom1 should get twice as
much CPU-time as xendom2. But:

xentop - 11:05:46   Xen 3.0.4-0
Mem: 2612284k total, 2603852k used, 8432k free    CPUs: 2 @ 2992MHz
      NAME  STATE   CPU(sec) CPU(%)  [...]
  Domain-0 -----r         42    0.6  [...]
   xendom1 ------        122   49.8  [...]
   xendom2 -----r        133   50.2  [...]

As you can see, both domains got an equal amount of the CPU.

Am i missing something or do i understand something wrong?

Timo Benk - Jabber ID: fry@xxxxxxxxxxxx - ICQ ID: #414944731
PGP Public Key: http://m28s01.vlinux.de/timo_benk_gpg_key.asc

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